Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 4 replies
  • Subscribers 32 subscribers
  • Views 1727 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Electrical Load Assesment - Total demand

Former Community Member
Former Community Member

Hi everyone,

Can you guys make some light into my head, please?

I have gotten very confused on how to do a load assessment for, let's say a building, that would have single-phase consumers as well as three-phase consumers. For this purpose and for easy understanding let's say we have sockets on single phases: L1 - 10A, L2 -12A, L3 -10A, and a three phase consumer of 30A. Can somebody show me a calc for getting the total demand in KVA please?

Parents
  • 0

    Calculate the KVA demand of each load and add them together.

    For example 10 amps=2.3 KVA presuming a 230 volt supply.

    A 3 phase 30 amp load will be about  7KVA on each phase or 21 KVA in total. In a real world example with numerous intermittent or variable  loads, the actual maximum demand may be less than that obtained by simple addition since it is unlikely that all loads will be used at the same time.

    On the other hand,  with only a few loads, simultaneous operation should normally be allowed for.

    Also remember that three phase supplies usually presume a balanced load.

    12 KVA on one phase, 12 KVA on the second phase and 40 KVA on the third phase does NOT mean that a 64 KVA supply will suffice. A 120 KVA supply would be needed (three times the load on the highest loaded phase)

    The LOAD would be 64 KVA, relevant when assessing running costs for example.

    But the SUPPLY needs to be 120 KVA.

Reply
  • 0

    Calculate the KVA demand of each load and add them together.

    For example 10 amps=2.3 KVA presuming a 230 volt supply.

    A 3 phase 30 amp load will be about  7KVA on each phase or 21 KVA in total. In a real world example with numerous intermittent or variable  loads, the actual maximum demand may be less than that obtained by simple addition since it is unlikely that all loads will be used at the same time.

    On the other hand,  with only a few loads, simultaneous operation should normally be allowed for.

    Also remember that three phase supplies usually presume a balanced load.

    12 KVA on one phase, 12 KVA on the second phase and 40 KVA on the third phase does NOT mean that a 64 KVA supply will suffice. A 120 KVA supply would be needed (three times the load on the highest loaded phase)

    The LOAD would be 64 KVA, relevant when assessing running costs for example.

    But the SUPPLY needs to be 120 KVA.

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines